LSAW Pipe: Definition and Manufacturing
LSAW stands for longitudinal submerged arc welded pipe (straight seam submerged arc welded pipe). It uses steel plate as the raw material: the plate is pressed or rolled into a tubular blank in a forming machine, then welded with double-sided submerged arc welding and finally mechanically cold-expanded. The finished product has complete specification coverage, and the weld has good toughness, plasticity, uniformity and density.
Because it starts from plate rather than coil, LSAW pipe offers the advantages of large pipe diameter, thick pipe wall, high pressure resistance, low-temperature toughness and corrosion resistance. It is the mainstream manufacturing route for large-diameter line pipe used in long-distance oil and gas pipelines.
LSAW Forming Methods
| Method | Process |
|---|---|
| UOE | Single plate: pre-bending, U-forming, O-forming, internal welding, external welding, mechanical cold expansion |
| JCOE | J-C-O-E progressive press forming, pre-welding, forming, post-weld cold expansion |
| HME | Formed by C-C-O using the mandrel rolling method; cold expanded after welding |
Size Range and Standards
Typical technical parameters for LSAW pipe:
Outer diameter:
Φ406.4 to Φ1422.4 mm, and beyond for special projects
Wall thickness:
6.4-23.8 mm for X80 grade; 6.4-26.4 mm for X70 grade; thicker walls are possible with lower grades
Length:
up to 12.2 m for X70 grade pipe
Standards:
API Spec 5L, ISO 3183, GB/T 9711 and equivalent line pipe standards
LSAW pipe is commonly supplied in grades from L245 (Grade B) through X70/X80, in both PSL1 and PSL2. It is the standard choice for high-pressure gas transmission trunk lines, offshore pipelines and large-diameter water transmission systems where ERW or SSAW cannot economically meet the diameter or toughness requirements.
Industrial Applications
Long-distance oil and gas transmission pipelines (onshore and offshore)
High-pressure gas trunk lines (e.g. X60-X80, PSL2 with Charpy testing)
Large-diameter water and slurry pipelines
Structural and offshore jacket applications where thick walls and high toughness are required
Frequently Asked Questions
What does LSAW stand for?
LSAW stands for longitudinal submerged arc welded pipe, meaning the weld seam runs along the pipe length and is made by submerged arc welding.
What is the difference between LSAW and SSAW?
LSAW has a straight longitudinal weld; SSAW (spiral submerged arc welded) has a helical weld. LSAW offers better weld uniformity and is preferred for high-pressure gas service.
What is the difference between LSAW and ERW?
LSAW is welded from plate with submerged arc welding and suits large diameters and thick walls; ERW is welded from coil with high-frequency resistance welding and suits smaller diameters and thinner walls.
What does UOE mean in LSAW production?
UOE describes the forming sequence: the plate is pressed into a U shape, then an O shape, welded, and mechanically expanded (E).
What diameter range does LSAW cover?
Typically Φ406.4 mm to Φ1422.4 mm, with larger diameters available for special projects.
Is LSAW pipe suitable for sour service?
Yes, when specified as PSL2 with controlled hardness and HIC/SSC testing per NACE MR0175 / ISO 15156; grade and weld qualification must be verified.
